Derivatives of triazolyl-imidazopyridine and of the triazolylpurines useful as ligandsof the adenosine a2a receptor and their use as medicaments

ABSTRACT

Compounds of formula (I) wherein the groups are as defined in the description, said compounds being antagonists of the adenosine A 2a  receptor and useful as medicaments, in particular for the treatment of Parkinson&#39;s disease are disclosed.

[0001] The present invention relates to derivatives oftriazolyl-imidazopyridine and of the triazolylpurines, useful as ligandsof the adenosine A_(2a) receptor, to a process for their preparation, totheir uses as medicaments, in particular, for the treatment ofpathologies which benefit from the inhibition of this receptor, and tothe pharmaceutical compositions comprising them.

BACKGROUND OF THE INVENTION

[0002] Current therapy for Parkinson's disease is limited to thealleviation of the symptoms, but no agent has yet been identifiedcapable of counteracting the establishment and the progress of thedegeneration of the dopaminergic neurons of the substantia nigra linkedwith deficient dopamine levels of the basal ganglia in turn responsiblefor the appearance of the complex symptomatology of this pathology. Thisis characterised by rigidity, tremors, bradykinesia, akinesia, posturechanges; manifestations that represent a serious threat to the health ofthe individual with Parkinson's disease.

[0003] Among the therapeutic strategies currently used to improve thequality of life of these subjects, are therapeutic approaches which aimto replenish the missing neurotransmitter. One example is represented bythe use of L-DOPA, in combination with carbidopa or benserazide(inhibitors of the peripheral amino acid decarboxylases enzymes). Thistherapy is one of the most effective and currently used against theappearance of changes in motor function which are manifested when thephysiology of the dopaminergic system is severely compromised.

[0004] However, in the long run, this therapeutic approach is subject toa lowering of efficacy. Indeed, patients subjected to chronic treatmentwith L-DOPA frequently display an emphasising of said manifestations, inaddition to the appearance of other side effects, due to the inherentlyneurotoxic properties possessed by L-DOPA.

[0005] Alternatively, the use of dopaminergic receptor agonists has beenintroduced, however they do not display the same efficacy as L-DOPA; orof monoamine oxidase inhibitors and of the muscarinic acetyl cholinereceptor antagonists. The use of the latter brings about the appearanceof serious side effects and cognitive impairment, as a consequence ofthe receptor interactions these products establish, both at the systemiclevel and at the central nervous system level.

[0006] In recent years, with the discovery of the role of adenosine as aneurotransmitter, its receptors and their functional characterisation,the hypothesis of using antagonists of the adenosine A_(2a) receptor astherapeutic agents for the treatment of the motor disorders associatedwith Parkinson's disease has gained credit. (P. J. Richardson, H. Kaseand P. G. Jenner Trends Pharm. Sci 1997, 18:338-345).

[0007] Recent experimental evidence has allowed the understanding of thedistribution, the function and the physiology of this receptor at thelevel of the central nervous system, permitting the conclusion thatblocking the A_(2a) receptor can modulate cholinergic, gabaergic andglutamatergic neurotransmission, in order to establish at the level ofthe basal ganglia output neurons, a neurochemical order which canadequately compensate acute or chronic Dopamine deficiency in thenigrostriatal system.

[0008] Furthermore, it has been observed that the A_(2a) receptor isfunctionally associated with that for Dopamine D₂ and that thestimulation of the former can reduce the binding capacity of the latterfor Dopamine. Thus it follows, that the blocking of the A_(2a) adenosinereceptor increases the interactive capacity of D₂ receptors towardsDopamine, favouring binding even in the presence of low levels of thisneurotransmitter in the synaptic space. (Ferre S., e al. (1991) Proc.Nat. Acc. Sci. U.S.A. 88, 7237-7241). For these reasons, selectiveantagonists of the A_(2a) receptor have been proposed as agents for thetreatment of motor disorders, with particular regard to Parkinson'sdisease.

[0009] In addition, it has been demonstrated that these agents offer aneffect that is synergic to the treatment with L-DOPA or with dopamineagonists, and can be used in conjunction with the Dopamine-substitutivetherapies. In this case, the use of receptor A_(2a) selectiveantagonists represents a further therapeutic advantage since, thedosages normally required for L-DOPA therapeutic treatment could bereduced in quantity, or frequency of administration, thereby conservingthe therapeutic efficacy.

[0010] The present invention relates to compounds with affinity for theadenosine A_(2a) receptor, active as antagonists, useful in thepreparation of medicaments for the treatment of motor disorders inindividuals, which are associated with functional alterations in thebasal ganglia, forming part of the symptomatology of diseases such asParkinson's disease, Alzheimer's disease, Huntington's disease andWilson's disease; brought about by drugs (parkinsonism of classicneuroleptics) trauma, toxic agents (NOTP, manganese, carbon monoxide).

[0011] The present invention can also be used in the treatment ofParkinson's disease with “on-off” phenomena and Parkinson's disease withpreponderant dyskinesia.

[0012] In addition, having been demonstrated that, following ischaemicdamage to the central nervous system, adenosine A_(2a) receptorantagonists can inhibit the toxic effects induced by the excitatoryamino acids released in abundance after such phenomena, cerebralischaemia and the mechanisms associated with neurodegenerative processesrepresent other “targets” towards which A_(2a) receptor antagonists candisplay their therapeutic actions.

[0013] Selective antagonists of the adenosine A_(2a) receptor aredescribed in CA 1.242.368, Boehringer Ingelheim, in the form ofimidazo-triazole-pyrimidine derivatives, in which their activity towardsthe A₁ receptor prevails towards the A₂ receptor; in WO 01/02409,Vernalis Res Ltd, derivatives of thieno- and furopyrimidine aredescribed as compounds useful in the treatment of motor disorders, forexample Parkinson; WO 00/24742, Fusijawa Pharm Co Ltd, describesderivatives of pyrazolopyridine with dual antagonistic action againstthe A₁ and A₂ receptors; WO 00/17201 and WO 98/42711, Kyowa Hakko KKK,describe derivatives of 1,2,4-triazolo-(1,5-c)pyrimidine; WO 00/13682,WO 00/13681 and WO 99/26627, Cerebrus Pharm Ltd, describe derivatives of4-quinolinemethanol; WO 99/62518, Cadus Pharm Corp, describe7-deazapurine N-6 substitutions with activity profiles as A₁, A₂,A_(2a), A_(2b), A₃ receptor antagonists; WO 99/43678, Kyowa Hakko KKK,describe derivatives of 1,2,4-triazolo-(1,5-a)-pyrimidine; WO 95/01356and WO 98/52568, Schering Plough SpA, describe1,2,4-triazolo-(1,5-c)-pyrimidine.

[0014] Amongst the A_(2a) receptor antagonists in advanced testingphase, we can mention compounds KW-6002 and KW-1783, described in EP 0628 311, which can be characterised as xanthine derivatives. Theseproducts possess a (3,4-dimethoxyphenyl)ethylenic group in position 8,and are subject to loss of activity through photoisomerisation of theethylenic bond (Annals New York Academy of Sciences—Ongini E.; Adami M;Ferri C; and Bertorelli R.; Trends in Pharm. Sci. 1996 Vol. 17 364-72).The compound KW 6002 is currently undergoing clinical trials (phase IIas an antidepressant and phase III as an antiparkinson agent;Pharmaprojects Acc. No. 23891). Another selective antagonist of the A₂areceptor is the product SCH 63390 (Pharmaproject Acc. No29842), inpre-clinical trials. ZM 241385 from Astra Zeneca (EP 0 459 702) is apotent selective antagonist; for this reason, utilised forpharmacological investigations (Ji X. D., Jacobson K. A., Drug Des.Discov. 1999, 16:217-226; Pharmaproject Acc. No 22730). Despite its highselectivity and affinity, in vivo the product has shown very lowbioavailability (El Yacoubi M.; et al Eur. J. Pharm. 401 (2000) 63-77).

SUMMARY OF THE INVENTION

[0015] It has been found that compounds with the formula

[0016] where: X is N, CH, C-R₂;

[0017] R₁ is C₁-C₆ linear or branched, saturated or unsaturated alkyl;

[0018] R₂ is hydrogen, C₁-C₆ linear or branched saturated or unsaturatedalkyl, C₆-C₁₄ aryl or C₆-C₁₄ aryl(C₁-C₆) linear or branched, saturatedor unsaturated alkyl with the aryl group optionally substituted by oneor more substituents, the same or different, selected from the groupconsisting of halogen, hydroxy, C₁-C₆ linear or branched, saturated orunsaturated alkoxy, amino, mono- or di- C₁-C₆ linear or branched alkyl;

[0019] R₃ is NH2, NHR₄

[0020] R₄ is C₁-C₆ alkyl or C₁-C₆ hydroxyalkyl, C₁-C₃ alkoxyalkyl,amino(C₁-C₆)alkyl, where the amino group is optionally substituted byone or two C₁-C₃ alkyl groups, said alkyl groups are either linear orbranched saturated or unsaturated, C₆-C₁₄ aryl or C₆-C₁₄aryl(C₁-C₆)alkyl, with the aryl group optionally modified by one or moresubstituents, the same or different, selected from the group constitutedby halogen, hydroxy, C₁-C₆ alkoxy linear or branched saturated orunsaturated, amino, mono- or di-substituted by C₁-C₆ alkyl linear orbranched saturated or unsaturated and pharmaceutically acceptable saltsthereof, possess affinity for the A_(2a) receptor.

[0021] Therefore, an object of the present invention are formula (I)compounds defined above and the pharmaceutically acceptable saltsthereof

[0022] Another object of the present invention are the processes for thepreparation of formula (I) compounds defined above, their use asmedicaments, in particular for the preparation of medicaments withinhibitory activity, also selectively, of the A_(2a) adenosine receptor,such medicaments being useful for the treatment of pathologiesresponsive to the inhibition of the adenosine A_(2a) receptor, such asthe treatment of motor disorders, Alzheimer's disease, Huntington'sdisease, Wilson's disease and Parkinson's disease. The compoundsaccording to the present invention are also useful for the preparationof medicaments for the treatment of cerebral ischaemia and/or themechanisms associated with neurodegenerative processes.

[0023] Further objects of the present invention are pharmaceuticalcompositions which contain at least one formula (I) compound as activeingredient.

[0024] This and other objects of the present invention will beillustrated in greater detail also by figures and examples, where:

[0025] in FIG. 1 it is shown the evaluation of the capacity to inducecatalepsy in mice;

[0026] in FIG. 2 it is shown the effect of exemplary compounds of thepresent invention on CGS 21680—induced catalepsy. Each column representsmean score catalepsy ± s.e. of 10 animals per group;

[0027] in FIG. 3 it is shown the effect of exemplary compounds of thepresent invention on Haloperidol-induced catalepsy, in mice. Each columnrepresents the mean catalepsy score ± s.e. of 10 animals per group;

[0028] in FIG. 4 it is shown the combination effects of exemplarycompounds of the present invention with sub threshold dose of L-DOPAplus benserazide (12.5 mg/kg and 6.25 mg/kg, i.p., respectively) onHaloperidol-induced catalepsy in mice;

[0029] in FIG. 5 it is shown the effect of exemplary compounds of thepresent invention in mouse forced swim test. Mice were injected withvehicle or the test compound or Imipramine 60 minutes before the test.

[0030] The duration of immobility was recorded during 4 minutes of thetesting period. Data represented are mean ± s.e. of 10 mice per group.ANOVA and Tukey's test **=p<0.01 vs. controls.

DETAILED DESCRIPTION OF THE INVENTION

[0031] In the formula (I) compounds, examples of C₁-C₆ saturated orunsaturated alkyls are methyl, ethyl, propyl, isopropyl, butyl,sec-butyl, ter-butyl, pentyl, hexyl, ethylene, propylene, butylene. Thealkenyls and the alkinyls may contain up to the maximum possible degreeof unsaturation, and the alkyls, alkenyls and alkinyls may berepresented by all the theoretically possible isomers. In the formula(I) compounds, examples of C₆-C₁₄ aryl or C₆-C₁₄ aryl(C₁-C₆)alkyl, withthe optionally substituted aryl group are phenyl, naphthyl and anthryl,at various bond positions (for example 1- or 2-naphthyl), benzyl,phenylethyl, phenylpropyl, phenylbutyl, phenylpentyl, phenylhexyl,arylalkyl analogues with naphthyl and anthryl, 2-, 3- or 4-phenyl groupssubstituted by the above mentioned groups, for example 2-, 3- or4-hydroxyphenyl, 2-, 3- or 4-alkoxyphenyl, where the alkyl residue is asdescribed above, 2-, 3- or 4-halophenyl, where the halogen is fluoro,chloro, bromo, iodo, 2-, 3- or 4-aminophenyl, where the amino group canbe mono or di substituted with an alkyl group as described above. Theperson skilled in the art will easily be able to characterise all thepossible compounds predicted for formula (I) defined above, making theappropriate substitutions with the definitions given for the variousgroups.

[0032] Pharmaceutically acceptable salts of formula (I) compounds areall these with organic or inorganic acids capable of salifying the basiccentres present, and which do not possess any toxic or otherwiseundesired effects.

[0033] Amongst the formula (I) compounds, a first preferred groupcomprises those wherein X is nitrogen and R₂ is a butyl group inposition 2.

[0034] A second preferred group is comprised of those wherein X isnitrogen and R₂ is a phenethyl group in position 2.

[0035] A third preferred group is comprised of those wherein X isnitrogen and R₂ is a pentyl group in position 2.

[0036] A fourth preferred group is comprised of those wherein X iscarbon and R₂ is hydrogen in position 6 or 7.

[0037] The following compounds are particularly preferred:

[0038] 6-amino-2,9-dimethyl-8-(triazol-2-yl)-9(H)-purine (ST 1491);

[0039] 2-butyl-9-methyl-8-(2H-1,2,3-triazol-2-yl)-9H-purine-6-ylamine

[0040] (ST 1535);

[0041]9-methyl-2-(2-phenylethyl)-8-(2H-1,2,3-triazol-2-yl)-9H-purine-6-ylamine(ST 1537);

[0042] 9-methyl-2-pentyl-8-(2H-1,2,3-triazol-2-yl)-9H-purine-6-ylamine(ST 2097).

[0043] As a particular case of the present invention, the compound6-amino-9-methyl-8-(triazol-2-yl)-9(H)-purine (ST 1490) revealedaffinity toward the A₁ adenosine receptor, therefore is useful for thepreparation of a medicament for the treatment of cognitive deficits,Alzheimer's disease, cerebral ischemia, acute and chronic renal failure,renal failure induced by radiografic contrast media or by cisplatin.

[0044] Formula (I) compounds can be prepared following the syntheticapproach described in the following diagram.

[0045] Compound a), obtainable through methods known in the literature,is subjected to be bromo-substituted at position 2, then the bromo issubstituted by the triazol-2-yl group.

[0046] The following diagrams 1A, 1Abis and 2A show, by way of exampleonly, the processes for the preparation of the compounds brieflydenominated ST 1491, ST 1536, ST 1535, ST 1537, ST 2097 and ST 1680.

[0047] The compounds indicated by the numbers (2) to (7) (diagrams 1Aand 1Abis) are obtained by synthetic procedures known in the literature,compound (1) is commercially available; compounds (8), (9) and (10), aredescribed in Heterocycles 1999, 721-726; J.Med.Chem.32, 11, 1989,2474-2485; J. Heter. Chem. 23, 3, 1986, 669-672; J. Chem. Soc. 1955,2755-2758; J. Med. Chem. 39, 2, 1996, 487-493; J. Heter. Chem. 27, 3,1990, 563-566; (11) and (12) are described in EP 0 082 369 but thepresent invention provides a new preparation. The molecules from (13) to(14) are new, therefore they are specifically claimed as intermediatesof the process described in the present invention. Persons skilled inthe art, resorting to their general knowledge and to the literature, areable to prepare the other formula (I) compounds, different from theseexemplified in the preceding diagrams.

[0048] The following examples further illustrate the invention.

EXAMPLE 1 Scheme 1A)

[0049] 2-chloro-6-dibenzylamino-9(H) Purine (2)

[0050] To a solution of 1 g of 2,6-dichloropurine (1) (97%, 5.13 mmol),in 30 ml of absolute ethanol were added di-isopropylethylamine (1 ml,5.13 mmol) and distilled dibenzylamine (1.1 ml, 5.13 mmol). The reactionmixture was left to reflux for 20 hours (after 1 hour a whiteprecipitate is formed). The solvent was then removed at low pressure andthe residue taken up in water.

[0051] Following cooling and filtration the solid residue (2), was driedunder vacuum.

[0052] Yield: 95%

[0053] R_(f)=0.25 (cyclohexane/ethyl acetate) 7:3

[0054] M.p.: 250-252° C.

[0055]¹H-NMR (200 MHz, CDCl₃): 67.89 (s, 1H), 7.32 (s, 10H), 5.55 (bs,2H), 5.49 (bs, 2H).

[0056] MS (m/z): 91; 258-260 (BP, M-benzyl), 349-351 (<5%, M).

[0057] 2-chloro-6-dibenzylamino-9-methyl-purine (3)

[0058] To a solution of (2) in hot DMF was added 828 mg of K₂CO₃ (6mmol). The solution was then cooled and treated with 0.46 ml of CH₃I(7.2 mmol) with agitation for about 12 hours. The DMF was evaporated,the product taken up in water and filtered, and the residue obtainedcrystallised in ethanol giving 1.45 g of product (3)

[0059] Yield: 78%.

[0060] Rf=0.38 (cyclohexane/ethyl acetate) 7:3.

[0061] M.p.: 144-146° C.

[0062]¹H-NMR (200 MHz, CDCl₃): ε 7.67 (s, 1H, H8-purine); 7.31 (s, 10H,aromatic); 5.5 (br, 2H, CH₂-benzylate); 4.93 (br, 2H, CH₂-benzylate);3.81 (s, 3H, CH₃).

[0063] MS (m/z): 91 (BP, benzyl); 272-274 (65%-20%, M-benzyl), 363-365(<5%, M).

[0064] 2-alkyl-6-dibenzylamino-9-methyl-9(H)-purine (4), (4c), (4e), (5)

[0065] (General procedure) In a nitrogen-filled flask were placed 700 mgof 2-chloro-6-dibenzylamino-9-methyl-9(H)-purine (3) (1.93 mmol), 4 mlof NMP (N-methylpyrrolidone), 3.8 mmol of alkyl tributyl tin and 140 mgof Pd(PPh₃)₄. These were stirred at 120° C., for 8 hours for compounds4, 4c and 4e and two hours for compound 5. These were cooled and dilutedwith water (50 ml) and methylene chloride (50 ml) and the aqueous phasefinally extracted with methylene chloride (4×50 ml). The combinedorganic phases were washed in salt water, dried over anhydrous sodiumsulphate and the solvent evaporated thus obtaining a dark liquid. Theproducts were purified on a silica-gel column, (eluent:EtOAc/Cyclohexane 1/1) giving (4), (4c), (4e) and (5) in the form ofsolids or yellow oils.

[0066] (4): Yield: 63%.

[0067] M.p.: 143° C.

[0068] MS (m/z): 278 (100%, M-benzyl); 91 (55%, benzyl).

[0069] (4c): Yield: 90%.

[0070] M.p.: non-determinable—rubber-like substance.

[0071] MS (m/z): 294 (100%, M-benzyl); 91 (65%, benzyl).

[0072]¹H-NMR: 200 MHz, CDCl₃; δ 7.65 (1H, s, purine); 7.30 (10H, m,aromatics); 5.27 (4H, br, —CH₂— benzylate); 3.82 (3H, s, N—CH₃); 2.88(2H, t, —CH₂—CH₂—CH₂—CH₃); 1.80 (2H, m, —CH₂—CH₂—CH₂—CH₃); 1.37 (2H, t,—CH₂—CH₂—CH₂—CH₃); 0.91 (3H, t, —CH₂—CH₂—CH₂—CH₃).

[0073] (4e) Yield: 65%.

[0074] 6-dibenzylamino-9-methyl-2-pentyl-9(H)-purine

[0075] M.p.: non-determinable, rubber-like substance.

[0076] MS: m/z=399, 308, 220 ¹H-NMR (200 MHz, CDCl3) δ (ppm): 7.71 (s,1H), 7.30 (m, 10H), 5.30 (bs, 4H), 3.80 (s, 3H), 3.38 (t, 2H), 2.38 (m,2H), 2.02 (m, 2H), 1.30 (m, 2H), 0.88 (m, 3H)

[0077] (5): Yield: 84%.

[0078] M.p.: non-determinable—rubber like substance. MS (m/z): 340(100%, M-benzyl); 91 (70%, benzyl).

[0079] 6-dibenzylamino-2,9-dimethyl-9(H)-purine (4a)

[0080] In a refrigerated, three-necked, round-bottomed flask, under aninert atmosphere (nitrogen), were placed 1.07 g of (3) (2.94 mmol)dissolved in 30 ml of anhydrous THF, 6 ml of trimethylaluminium 2M intoluene (12 mmol), 27 mg of PdCl₂ (0.15 mmol) and 79 mg of PPh₃ (0.3mmol). These were reacted by refluxing for 48 hours. Terminating thereaction, the mixture was poured into a beaker, chilled in an ice bathand the excess trialkylaluminium destroyed by small additions of waterand alcohol. The aluminium hydroxide precipitate was filtered throughpaper, and the mixture extracted with dichloromethane. Followingevaporation of the organic phase at reduced pressure the residue waspurified by flash chromatography (SiO₂, cyclohexane/EtOAc 1:1). 900 mgof (4a) (2.62 mmol) in crystalline form were obtained.

[0081] Yield 89%.

[0082] M.p.: 117-118° C.

[0083] MS (m/z): 91 (80%, benzyl), 252 (BP M-benzyl), 343 (<5%, M).

[0084]¹H-NMR: 200 MHz, CDCl₃ δ 7.65 (s, 1H, H8-purine); 7.30 (s, 10H,aromatics); 5.30 (br, 4H, CH₂-benzylate); 3.81 (s, 3H, N—CH₃); 2.62(s,3H, C—CH₃).

[0085] 2-isoproyl-6-dibenzylamino-9-methyl-9(H)-purine (4b) and2-(2-phenylethyl)-6-dibenzylamino-9-methyl-9(H)-purine (4d)

[0086] 100 mg of (4) or (5) were placed in an autoclave with 5 ml ofethanol, heated until completely dissolved and then 50 mg of palladiumon graphite support added. This was left stirring overnight under 4atmospheres of hydrogen. The catalyst was filtered through celite andthe solvent evaporated under reduced pressure, giving (4b) or (4d) aswhite solids.

[0087] (4b): Quantitative yield.

[0088] M.p.: 82° C.

[0089] MS m/z: 280 (100%, M-benzyl); 91 (50%, benzyl).

[0090] (4d): Quantitative yield.

[0091] M.p.: 144° C.

[0092] MS m/z: 342 (100%, M-benzyl); 91 (100%, benzyl).

Scheme 1A bis

[0093] (5a,b,c,d,e)

[0094] General Procedure

[0095] In a reaction flask were solubilised 1.6 mmol of (4a), (4b),(4c), (4d) and (4e) in a mixture of 7 ml of MeOH, 7 ml of THF and 7 mlof acetate buffer pH=4 (obtained by dissolving 4 g of sodium acetate in100 ml of water and bringing to pH 4 with glacial acetic acid). 0.7 mlof bromine (13.6 mmol) were added very slowly dropwise and the mixtureleft at room temperature under stirring until the starting products haddisappeared (about 12 hours). Excess bromine was decoloured with sodiummetabisulphite and the reaction alkalinised to pH=8 with a saturatedsolution of Na₂CO₃. After extraction with dichloromethane andevaporation of the solvent at reduced pressure, 1.2 g of yellow oil wereobtained for (5a), (5b), (5c), (5d) (5e), later purified on preparativechromatographic column.

[0096] (5a): Quantitative yield.

[0097] MS m/z: 91 (100%, benzyl); 330-332 (doublet, 70%, M-benzyl).

[0098] (5b): Quantitative yield.

[0099] MS (m/z): 91 (100%, benzyl); 358-360 (doublet, 70%, M-benzyl).

[0100] (5c): Quantitative yield.

[0101] MS m/z: 91 (100%, benzyl); 372-374 (doublet, 70%, M-benzyl).

[0102] (5d): Quantitative yield.

[0103] MS (m/z): 91 (100%, benzyl); 420-422 (doublet, 45%, M-benzyl).

[0104] (5e)

[0105] 9-bromo-6-dibenzylamino-9-methyl-2-pentyl-9(H)-purine

[0106] M.p.: 97° C.

[0107] MS: m/z=479-477, 388-386

[0108]¹H-NMR (200 MHz, CDCl₃) δ (ppm): 7.28 (m, 10H), 5.16 (bs, 4H),3.75 (s, 3H), 2.79 (t, 2H), 1.79 (m, 2H), 1.29 (m, 4H), 0.86 (m, 3H)

[0109] 2-Alkyl-6-dibenzylamino-9-methyl-8-(triazol-2-yl)-9(H)-purine(6a,b.c.d,e)

[0110] In a reaction flask, under an inert atmosphere, were placed 2 mlof anhydrous DMF, 92 mg of NaH (80% in paraffin, 2.5 mmol) and slowly,0.18 ml of 1,2,3-triazole (2.5 mmol) were added and left under stirringfor about 1 hour. A solution of crude (5a),(5b), (5c), (5d) or (5e) (1.7mmol) in 5 ml of anhydrous DMF was added dropwise, slowly and left understirring at 100° C. for 12 hours. The DMF was evaporated and the residuepurified by flash chromatography (SiO₂, cyclohexane/EtOAc 7:3) giving(6a), (6b), (6c), (6d) or (6e) as white solids.

[0111] (6a): Yield: 20%.

[0112] M.p.: 161-163° C.

[0113] MS (m/z):91 (90%, benzyl), 319 (BP, M-benzyl); 410 (<5%, M).

[0114]¹H-NMR: 200 MHz, CDCl3: δ 7.94 (s, 2H, H-triazole); 7.29 (s, 10Haromatics); 5.45 (br, 2H, CH₂-benzylate); 5.04 (br, 2H, CH₂-benzylate);3.96 (s, 3H, N—CH₃); 2.62 (s, 3H, C—CH₃).

[0115] (6b): Yield 20%.

[0116] M.p.: 140° C.

[0117] MS (m/z): 347 (100%, M-benzyl); 91 (75%, benzyl).

[0118] (6c): Yield 20%.

[0119] M.p.: 114° C.

[0120] MS (m/z): 361(100%, M-benzyl); 91(70%, benzyl).

[0121]¹H-NMR: 200 MHz, CDCl₃; δ 7.94 (2H, s, triazole); 7.30 (10H, m,aromatics); 5.49-5.21 (4H, d, br, —CH₂— benzylate); 4.12 (3H, s, N—CH₃);2.84 (2H, t, —CH₂—CH₂—CH₂—CH₃); 1.80 (2H, m, —CH₂—CH₂—CH₂—CH₃); 1.37(2H, m, —CH₂—CH₂—CH₂—CH₃); 0.92 (3H, t, —CH₂—CH₂—CH₂—CH₃).

[0122] (6d): Yield 20%.

[0123] M.p.: 173° C.

[0124] MS (m/z): 409 (65%, M-benzyl), 91 (100%, benzyl).

[0125] (6e)

[0126] 6-dibenzylamino-9-methyl-2-pentyl-8-(triazol-2-yl)-9(H)-purine

[0127] M.p.: 139° C.

[0128] MS: m/z=466, 375, 348

[0129]¹H-NMR (200 MHz, CDCl₃) δ (ppm): 7.94 (s, 2H), 7.29 (m, 10H), 5.47(bs, 2H), 5.04 (br, 2H), 3.96 (s, 3H), 2.84 (t, 2H), 1.82 (m, 2H), 1.33(m, 4H), 0.88 (m, 3H)

[0130] 2-Alkyl-6-amino-9-methyl-8-(triazol-2-yl)-9(H)-purine(7a,b,c,d,e)

[0131] In a refrigerated reaction flask under nitrogen, were dissolved0.33 mmol of (6a), (6b), (6c), (6d) or (6e) in 3 ml of anhydrousdichioromethane. 0,37 ml of CF₃SO₃H (3.3 mmol) were added slowly,dropwise, and the mixture left refluxing for six hours. The mixture wasthen loaded onto an activated alumina chromatographic column, firstlyeluted with 50 ml of dichloromethane to eliminate the strongly colouredaromatic derivatives, and then with CH₂Cl₂/ethanol 1:1 (40 ml), followedby ethanol (40 ml) and finally with saturated aqueous ammonia in ethanol(5%, 40 ml). The moieties containing the desired product were combinedand evaporated, giving a yellow solid which was purified by flashchromatography (SiO₂, AcOEt/EtOH 95:5), giving the pure products(7a,b,c,d,e) as white solids. Crystallisation in ethanol gave highlypure product in the form of small, very white crystals. (7c) (ST 1535)

[0132] Yield: 55%.

[0133] M.p.: 182° C.

[0134] MS (m/z): 230 (100%, M-42); 243 (20%, M-29); 257 (10%, M-15); 272(<10%, M).

[0135]¹H-NMR: 200 MHz, CDCl₃; δ 8.00 (2H, s, triazole); 5.74 (2H, br,—NH₂); 4.07 (3H, s, N—CH₃); 2.85 (2H, t, —CH₂—CH₂—CH₂—CH₃); 1.79(covered by water, m, —CH₂—CH₂—CH₂—CH₃); 1.43 (2H, m, —CH₂—CH₂—CH₂—CH₃);0.97 (3H, t, —CH₂—CH₂—CH₂—CH₃).

[0136] (7b) (ST 1536)

[0137] Yield: 55%.

[0138] M.p.: 177° C. ¹H-NMR: (200 MHz, CDCl₃) δ 8.00 (2H, s, triazole);5.70 (2H, br, —NH₂); 4.07 (3H, s, N—CH₃); 3.10 (1H, sextuplet (J=6.82Hz), CH₃—CH—CH₃); 1.36 (6H, d (J=6.82 Hz), CH₃—CH₂—CH₃). MS: m/z: 230(100%, M-28); 243 (95%, M-15); 216 (50%, M-44); 258(50%, M).

[0139] (7d) (ST 1537)

[0140] Yield: 55%.

[0141] M.p.: 164° C.

[0142]¹H-NMR (200 MHz, CDCl₃): δ 8.00 (2H, s, triazole); 7.3-7.18 (5H,m, arom.); 4.07 (2H, s, CH₂); 3.17 (2H, s, CH₂); 1.26 (3H, s, CH₃). MSm/z: 91, 216, 243, 303, 320 (100%, M).

[0143] (7a) (ST 1491)

[0144] Yield: 43%.

[0145] M.p.: 238° C.

[0146] MS (m/z): 230 (BP, M).

[0147]¹H-NMR (200 MHz, CDCl₃): δ 8.00 (s, 2H triazole); 5.63 (br, 2H,NH₂); 4.06 (3H, s, N—CH₃); 2.64 (3H, s, C—CH₃).

[0148] (7e) (ST 2097)

[0149] 6-amino-9-methyl-2-pentyl-8-(triazol-2-yl)-9(H)-purine

[0150] M.p.: 154° C.

[0151] MS: m/z=286, 271, 257, 243, 230, 190

[0152]¹H-NMR (200 MHz, CDCl₃) δ (ppm): 8.00 (s, 2H), 7.26 (m, 10H), 5.56(bs, 2H), 4.06 (s, 3H), 2.83 (t, 2H), 1.84 (m, 2H), 1.40 (m, 4H), 0.91(m, 3H).

EXAMPLE 2 Scheme 2

[0153] 4-hydroxy-3-nitropyridine (8)

[0154] 16.7 ml of oleum (SO₃ 20% in H₂SO₄) was added slowly and dropwiseto 20 ml of fuming nitric acid chilled to 0° C., and over a period of 15minutes, 7 g of 4-hydroxypyridine were added. This was heated slowlyuntil nitration began (red vapours developed). The reaction was thencooled until said vapours disappeared, then refluxed for 1 hour.

[0155] The reaction mixture was slowly cooled to room temperature andthen poured over 50 g of ice. 60 ml of concentrated aqueous ammonia(30%) was added in small doses, taking care the temperature did not riseabove 20° C. The pH was adjusted to 7.5 with more ammonia and then leftat 4° C. overnight. The precipitate produced was filtered andcrystallised in water to obtain 7.1 g of (8) as clear yellow crystals.

[0156] Yield=70%.

[0157] M.p.: 275-277° C.

[0158] MS (m/z): 94, 140.

[0159] 4-chloro-3-nitropyridine (9)

[0160] In a reaction flask under nitrogen, were reacted at 70° C., 51.5g of PCl₅ and 75 ml of POCl₃. At the same temperature was addedcarefully 34.6 g of (8). The temperature was increased to 140° C. andthe reaction refluxed for 4 hours under nitrogen. To the cooled mixture,evaporated under vacuum, was added 100 ml of iced water. The pH wasadjusted to 7.5 by the addition of granular sodium carbonate, and 60 mlof methylene chloride added and the mixture stirred vigorously until allthe residue had completely dissolved. The phases were separated and theaqueous part was extracted with more methylene chloride (5×30 ml). Thecombined organic phases were treated with anhydrous sodium sulphate andevaporated to obtain 29.9 g of (9) as a yellow, waxy solid.

[0161] Yield=76%.

[0162] MS (m/z): 85, 87, 100, 102, 112, 114, 158, 160 (M).

[0163] 4-methylamino-3-nitropyridine (10)

[0164] 29.9 g of (9) were solubilised in 200 ml of hot ethanol; to thesolution, brought to 0° C., were added slowly, dropwise, 103 ml of 35%aqueous methylamine. This was left stirring for 30 minutes and then theethanol evaporated. The residue was crystallised in water giving 24 g of(10) in the form of clear yellow crystals.

[0165] Yield=83%.

[0166] MS (m/z): 107, 120, 135, 153 (M).

[0167] 2-chloro-4-methylamino-3-aminopyridine (11)

[0168] 10 g of (10) were dissolved in 50 ml of 12N HCl and thetemperature brought to 90° C. 72.5 g di SnCl₂.2H₂O were added in fiveportions over the course of 1 minute. This was left stirring at 90° C.for 1 hour. After cooling the solution to room temperature, 100 ml ofwater were added and evaporated at reduced pressure. The residue wastaken up in 100 ml of water, cooled to 0° C. and concentrated aqueousammonia added, until the formation of a white, gelatinous precipitate.The pH was adjusted to 8.5-9 and the resulting emulsion centrifuged. Theremaining solid residues were again taken up in water and centrifuged.The operation was repeated three times. The combined solid residues wereleft under stirring overnight in 50 ml of methylene chloride. Thecentrifuged aqueous phases were extracted three times with methylenechloride, then all the organic phases combined, then dried overanhydrous sodium sulphate and subsequently evaporated under vacuum,giving 6.2 g of (11) in the form of pink crystals.

[0169] Yield=60%.

[0170] M.p.: 166-168° C.

[0171] MS (m/z): 76, 122, 142, 157(M+).

[0172] 4-chloro-1-methyl-1(H)-imidazo[4.5-c]pyridine (12)

[0173] 2,4 g of (11) were suspended in 97 ml of ethyl orthoformate, andDMF added with agitation until the turbidity disappears. To the clearsolution obtained was then added 1.7 ml of 12N HCl. (after a few minutesof the addition of the acid, the solution becomes turbid) and left understirring, under nitrogen for 12 hours. The solvent was then evaporatedunder vacuum and the brown oily residue purified by flash chromatography(eluent: cyclohexane/ethyl acetate 20:80) giving 1.7 g of (17) as awhite solid.

[0174] M.p.: 137-38° C.

[0175] Yield=68%.

[0176] MS: m/z: 167-169 (100%-30%: M+); 132 (55%: M+—Cl); 105 (35%).

[0177]¹H-NMR (200 MHz, CDCl₃): δ 3.91 (s, 3H, N—CH₃); 7.33 (d, J=5.64Hz, 1H, ═N—CH═CH—), 7.98 (s, 1H, —N═CH—N(CH₃)—), 8.24 (d, J=5.64 Hz, 1H,═N—CH═CH—).

[0178] 2-bromo-4-chloro-1-methyl-1 (H)-imidazo[4.5-c]pridine (13)

[0179] 1.5 g (9 mmol) of (12) were solubilised, under nitrogen, in 25 mlof anhydrous THF and the temperature of the mixture adjusted to —78° C.8 ml of BuLi 2.5 M (20 mmol) in hexane was added slowly. The solutiontook on a reddish colour in testimony to the formation of an aromaticcarbanion in position 2. After 1 hour, 2 ml of bromine (40 mmol) werecarefully added dropwise, over a period of 30 minutes and then left withagitation for a further 2 hours. The temperature was brought slowly to0° C. and then a saturated solution of sodium metabisulphite addeddropwise until the bromine was completely destroyed. The pH of thesolution was adjusted to 9 with aqueous 2N sodium bicarbonate. Thesolution was extracted with methylene chloride. The combined organicphases were washed with salt water, dried over anhydrous sodium sulphateand evaporated under vacuum. A brownish solid was obtained whichcrystallised in water giving 1.4 g of (13) in the form of whitecrystals.

[0180] Yield=64%.

[0181] MS: m/z: 245-247-249 (80%-100%-25%: M+); 210-212 (80%-75%:M+—Cl); 131 (100%: M+—Cl—Br), 105 (50%).

[0182]¹H-NMR (200 MHz, CDCl₃): δ 3.84 (s, 3H, N—CH₃); 7.25 (d, J=6.11Hz, 1H, ═N—CH═CH—), 8.23 (d, J=6.11 Hz, 1H, ═N—CH═CH—).

[0183] 4-chloro-1-methyl-2-(triazol-2-yl)-1(H)-imidazo[4,5-c]pyridine(14) and 4-chloro-1-methyl-2-(triazol-1-yl)-1(H)-imidazo[4,5-c]pyridine(14a)

[0184] 250 mg of NaH (80% in paraffin, 8.6 mmol) were suspended in 5 mlof anhydrous DMF and 0.5 ml (8.6 mmol) of 1(H)-1,2,3-triazole added.This was left under stirring at room temperature for one hour, then thetemperature adjusted to 100° C. To this hot solution was added dropwise,over the course of 30 minutes, 1.4 g (5.7 mmol) of (13) emulsified in 15ml of hot, anhydrous DMF. This was left under stirring at 100° C. for 4hours, and then the temperature reduced to 60° C., and left to reactovernight.

[0185] Upon termination of the reaction the DMF was evaporated and thesolid residue crystallised in water.

[0186] The crystals were collected by filtration and the mother liquorextracted with methylene chloride, the organic phases combined and driedover sodium sulphate, evaporated and re-crystallised again in water. 614mg of a mixture of (14 and 14a) were obtained, in the form of whitecrystals.

[0187] Total yield=46% (14+14a).

[0188] (14):

[0189] MS (m/z): 234-236 (100%-30%: M+); 207-209 (20%-5%: M+—HCN);153-155 (40%-10%).

[0190]¹H-NMR (CDCl₃, 200 MHz): δ 4.13 (s, 3H, N—CH₃); 7.35 (d, J=5.62Hz, 1H, ═N—CH═CH—), 8.05 (s, 2H, Triazole), 8.33 (d, J=5.62 Hz, 1H,═N—CH═CH—).

[0191] (14a):

[0192] MS (m/z): 234-236 (10%-3%: M+); 206-208 (100%-35%: M+—N₂);191-193 (40%-15%).

[0193]¹H-NMR (CDCl₃, 200 MHz): δ 4.23 (s, 3H, N—CH₃); 7.39 (d, J=5.80Hz, 1H, ═N—CH═CH—), 7.93 (d, J=1.19 Hz, 1H, Triazole), 8.34 (d, J=5.80Hz, 1H, ═N—CH═CH—), 8.65 (d, J=1.19 Hz, 1H, Triazole).

[0194]4-benzylamino-1-methyl-2-(triazol-2-yl)-1(H)-imidazo[4,5-c]pyridine(15).

[0195] In a flat-bottomed, long-necked reaction flask was suspended 1.4g (5.5 mmol) of mixture (14,14a), in 5 ml of benzylamine. The reactionwas placed inside a microwave oven (frequency of irradiation: 2,450 MHz)and irradiated at 460 Watts until the benzylamine boiled. This wasboiled for a few seconds and then the irradiation stopped and themixture allowed to cool. This operation was repeated until the startingproducts had disappeared, as monitored by TLC. Following cooling, ayellow waxy mass was obtained which was further purified by flashchromatography (gradient: cyclohexane/ethyl acetate 4:6 (100 ml),cyclohexane/ ethyl acetate 2:8 (100 ml), ethyl acetate). 390 mg of (15)was obtained as a yellow solid.

[0196] Yield=29%.

[0197] M.p.=180-184° C.

[0198] MS (m/z): 305 (BP, M+); 250; 200, 174, 148.

[0199]¹H-NMR (CDCl₃, 200 MHz): δ 4.02 (s, 3H, N—CH₃); 5.87 (bs, 2H),7.29 (d, J=6.90 Hz, 1H), 7.40-7.50 (m, 5H) 7.88 (d, J=6.90 Hz, 1H), 8.29(s, 2H, Triazole).

[0200] 4-amino-1-methyl-2-(triazol-2-yl)-1(H)-imidazo[4,5-c]pyridinoTriflate (16) (ST 1680)

[0201] 183 mg of (15) (0.6 mmol) were dissolved in 5 ml of anhydrousmethylene chloride and 0.7 ml of trifluoromethanesulphonic acid (6 mmol)added slowly, dropwise. This was left to reflux for 1.5 hours. Thereaction mixture was then chromatographed on an alumina column, elutedfirst with methylene chloride (100 ml), then with methylenechloride/ethanol 50/50 (100 ml) and finally with pure ethanol. Thedesired products were recovered in the alcoholic moieties. Followingevaporation of the solvent, the residue was triturated using ethyl etherand then crystallised in ethanol. 52 mg of pure ST 1680, were obtained.

[0202] Yield=24%.

[0203] M.p.: >290 (dec.)° C.

[0204] MS (of the free base): m/z: 215 (100%: M+); 160 (40%-5%); 134(35%).

[0205]¹H-NMR (DMSO-d6, 200 MHz): δ 3.99 (s, 3H, N—CH₃); 7.37 (d, J=6.84Hz, 1H, ═NH+—CH═CH—), 7.82 (d, J=6.84 Hz, 1H, ═NH+—CH═CH—), 8.41 (s, 2H,Triazole), 8.62 (br, 1H, NH2), 12.94 (s, 2H, ═NH+CH═CH—).

[0206] The compounds according to the present invention are ligands ofthe adenosine A_(2a) receptor, in particular, they are selectiveantagonists, and as such are useful as medicaments, in particular forthe treatment of pathologies benefiting from an antagonistic activitytowards the A_(2a) receptor.

[0207] Amongst the pathologies treated with the compounds of the presentinvention are motor disorders. As pathologies treated by the presentinvention we cite Alzheimer's disease, Huntington's disease, Wilson'sdisease and Parkinson's disease.

[0208] The present invention is also applied to Parkinson's diseaseassociated with “on-off” phenomena, with preponderant dyskinesia.

[0209] In a preferred embodiment of the present invention, the compoundsdescribed are in combination with L-DOPA or with one or more dopamineagonists. In this case, the present invention is useful in dopaminesubstitutive therapy.

[0210] In another embodiment of the present invention, the compoundsdescribed above are useful as active ingredients for the preparation ofa medicament for the treatment of cerebral ischaemia and-or themechanisms associated with neurodegenerative processes.

[0211] Molecular Pharmacology

[0212] Affinity Towards the Adenosine A_(2a) Receptor

[0213] The interactive capacity of each product towards the adenosineA_(2a) receptor was evaluated using membranes from HEK 293 cells (humanembryo kidney cells) stably expressing the human A_(2a) receptor subtypeexclusively.

[0214] The membranes were incubated with [3H]-CGS21680 at aconcentration of 30 nM in a buffer comprised of 50 mM Tris (pH 7.4); 120mM NaCl; 10 mM MgCl₂ mM CaCl₂, 2 U/ml of adenosine deaminase for 90′ at25° C. Non-specific binding was measured in the presence of NECA (50μM).

[0215] Affinity Towards the Adenosine A_(2b) Receptor

[0216] The interactive capacity of each product towards the adenosineA_(2b) receptor was evaluated using membranes from HEK 293 cells stablyexpressing the human A_(2b) receptor subtype exclusively.

[0217] These membranes were incubated with [³H]-DPCPX at a concentrationof 100 nM in a buffer comprised of 50 mM Tris (pH 7.4); 120 mM NaCl; 5mM KCl; 10 mM MgCl₂; 2 mM CaCl₂, 2 U/ml of adenosine deaminase for 90′at 25° C. Non-specific binding was measured in the presence of NECA (50μM).

[0218] Affinity Towards the Adenosine A₁ Receotor

[0219] The interactive capacity of each product towards the adenosine A₁receptor was evaluated using membranes from CHO-K1 cells which stablyexpress the human A₁ subtype.

[0220] These membranes were incubated with [3H]-DPCPX at a concentrationof 1.66 nM in a buffer comprised of 50 mM Tris (pH 7.4); 120 mM NaCl; 5mM KCl; 10 mM MgCl₂; 2 mM CaCl₂, 2 U/ml of adenosine deaminase for 90′at 25° C. Non-specific binding was determined in the presence of DPCPX(8-Cyclopentyl-1,3-dipropylxanthine) at a concentration of 1 μM.

[0221] Affinity Towards the Adenosine A₃ Receptor

[0222] For compounds ST 1535 and ST 2097 their affinities towards theadenosine A₃ receptor were determined.

[0223] For this study, membranes from HEK-293 cells, which stablyexpress the human A₃ subtype, were used, according to the methoddescribed by Salvatore et al. Proc. Natl. Acad. Sci. USA, 199990:10365-10369. The experimental conditions required the use of[¹²⁵I]AB-MECA as a radioligand at a concentration of 0.1 nM, anincubation time of 90 minutes at a temperature of 22° C., and IB-MECA (1μM) for the determination of non-specific binding.

[0224] Analysis and Expression of the in Vitro Results

[0225] In binding studies for each compound, eight differentconcentrations (from 10⁻⁵ M to 10⁻¹² M) were evaluated in order toobtain competition curves. By means of non-linear regression analysis ofthe competition curves, the IC₅₀ values, which express the bindingaffinity of each product, were determined. Using the Cheng Prusoffequation (K_(i)=IC₅₀/1+(L/K_(d))) K_(i) values were calculated throughwhich the affinity of each product studied, for the receptorinvestigated, is expressed.

[0226] General Pharmacology

[0227] Evaluation of the Effects on Spontaneous Motor Activity in Mice

[0228] For this study, type CD1 male mice (n=8) were used. The effectsof the products under study and of the reference compounds wereevaluated using an apparatus consisting of a Plexiglas cage (40 cm×40cm) surrounded by a series of photocells which monitor the movements ofthe animals placed inside, connected a computerised system, throughwhich, the signals are collected and later elaborated.

[0229] Tests were carried out, after endoperitoneal administration ofthe products. 15 minutes after treatment, the treated animals,alternating with the controls, were placed inside the cage so as torecord their spontaneous movements over a total period of 45 minutesbroken down into two observation intervals (15′-45′ and 45′-60′, withrespect to the time after treatment).

[0230] To examine the possible effects of the compounds studied on motoractivity, the following parameters were considered: horizontal activity,vertical activity: total distance.

[0231] Except for CGS 21680 (reference compound, described in EP 0 277917, Ciba-Geigy) which was dissolved in 0.9% NaCl, the products studiedwere solubilised in DMSO and then diluted in Cremofor EL and 0.9% NaCl(final concentrations: DMSO 15%, Cremofor EL 15%, NaCl 0.9

[0232] Evaluation of the Capacity of the Products to Induce Catalepsy inMice.

[0233] 10 CD1 male mice were used per group. For this test, a steel bar,10 cm long, was placed at a height of 4.5 cm above the support surface.Onto this, were placed the front legs of the animals. The presence ofcatalepsy was determined by measuring the time (in seconds) the animalremained in the posture placed. Later, this parameter was placedrelatively, on a scale of rising values (0 to 5) through which, thedegree of catalepsy determined in both control animals and in thesesubjected to treatment with the substances under test could beproportionately expressed.

[0234] The reference products and these in this study were administeredendoperitoneally, in a volume of 10 ml/kg, 30 minutes prior to the test.

[0235] Except for CGS 21680 (reference compound) which was dissolved in0.9% NaCl, the products in the study and the control antagonist ZM241385 were solubilised in DMSO and then diluted in Cremofor EL and 0.9%NaCl (final concentrations: DMSO 15%, Cremofor EL 15%, NaCl 0.9%).

[0236] Evaluation of the Capacity of the Products to Antagonise CGS21680 Induced Catalepsy

[0237] For this study, the product ST 1535 was used. Catalepsy wasinduced in the animals through the intracerebroventricularadministration of CGS 21680 (10 μg/5 μl/mouse), 30 minutes prior totesting for the catalepsy score. The test compound was administeredorally at a dose of 5 mg/Kg and 10 mg/Kg, 30 minutes prior to treatmentwith CGS 21680.

[0238] The catalepsy score was derived in the manner described followingtreatment with OGS 21680 after the following times: 30′, 60′120′, 180′.

[0239] Evaluation of the Capacity of the Products to AntagoniseHaloperidol-Induced Catalepsy

[0240] For this study, product ST 1535 was used. Catalepsy was inducedin the animals through the endoperitoneal administration of Haloperidolat a dose of 4 mg/Kg, two hours prior measuring catalepsy in theanimals, the presence of which was determined according to the methoddescribed previously.

[0241] After scoring for catalepsy by Haloperidol, the animals weretreated orally, with a dose equal to 10 mg/kg and 20 mg/kg of theproduct ST 1535. Then 60 minutes after treatment, the animals weresubjected to further catalepsy scoring, which was carried out at thefollowing times after ST 1535 administration: 120′, 240′, 300′.

[0242] Effect of the Administration of Associated L-DOPA and A_(2a)Antagonists on Haloperidol-induced Catalepsy.

[0243] For this study, product ST 1535 was used.

[0244] CD1 mice, divided into different experimental groups (n=10 pergroup) were used. All animals were subjected to treatment withHaloperidol (4 mg/kg, i.p.) two hours and 30′ prior to the catalepsytest, carried out according to the method described above.

[0245] Later, the animals were subjected to different types of treatmentaccording to their original experimental group (see diagram). Allcatalepsy evaluations were carried out 2 hours and 30 minutes afterHaloperidol treatment.

[0246] Haloperidol+ST 1535: ST 1535 2.5 mg/kg, per os, 75′ prior totesting;

[0247] Haloperidol+benserazide+L-Dopa: Benserazide 3.12 mg/kg i.p., 90′prior to testing;

[0248] L-DOPA: 12.5 mg/kg, 60′ prior to testing;

[0249] Aloperidol+benserazide+L-Dopa+ST 1535: Benserazide 3.12 mg/kgi.p., 90′ prior to testing;

[0250] ST 1535 1.25 mg/kg or 2.5 mg/kg, 75′ prior to testing; L-DOPA12.5 mg/kg, 60′ prior to testing;

[0251] A_(2a) Antagonists and Antidepressant Activity. Forced Swim Testin Mice

[0252] Mice were dropped individually into glass cylinders (height: 25cm, internal diameter.10 cm) containing 10 cm water, maintained at 23°C. The immobility time (sec) was measured during 4 minutes of test. Amouse was judged to be immobile when it remained floating in the water,making only the necessary movements to keep its head above water. Testcompound ST 1535 was administered orally to mice, 60 minutes before thetest.

[0253] In Vitro Activity

[0254] Table 1 reports values of the mean and standard deviations of theaffinity towards the adenosine A_(2a) receptor, expressed as K_(i) (nM)for the various compounds studied.

[0255] It is possible to observe that the products denominatedrespectively ST 1535, ST 1537 and ST 2097 exhibit elevated interactivecapacity towards the adenosine A_(2a) receptor.

[0256] The comparison of the affinity values of these compounds, withthese relative to the other products with adeninic structures, denotesthat the substitution of adenine in position two, with relatively longalkyl chains (see ST 1535, ST 2097) or with significant steric hindrance(see ST 1537), favours an increase in affinity towards the A_(2a)receptor.

[0257] In the same table are reported affinity values towards theadenosine receptor subtypes A_(2b) and A₁, of each compound studied and,the ratio of receptor affinity (K_(i)A₁/K_(i)A_(2a)), through which isdetermined the selectivity of each product.

[0258] It is observed that compounds ST 1535, ST 1537 and ST 2097possess an interactive capacity for the A_(2a) receptor prevalent withrespect to that demonstrated towards the A₁ and A_(2b) subtypes,therefore, the compounds according to the present invention possessselective affinity towards the A_(2a) receptor.

[0259] Furthermore, for compounds ST 1535 and ST 2097 the affinity forthe adenosine A₃ receptor and for 36 receptors belonging to otherneurotransmitters have been evaluated. In these binding studies,compounds of interest were initially tested at a concentration of 1 μM.Later, if the compound displaced more than 50% of the specificradioligand it was evaluated at 8 different product concentrations todetermine the IC₅₀ values.

[0260] The results relating to this binding study are reported in table2.

[0261] Compounds ST 1535 and ST 2097 display relatively low andnegligible affinity towards the adenosine A₃ subtype and have nointeractive capacity towards the other receptors (IC₅₀>1000 nM).

[0262] These results demonstrate that the compounds in the presentinvention are selective, having selective affinity for the adenosineA_(2a) receptor. TABLE 1 A_(2a) A_(2b) A_(t) Compound K_(i) (nM) ± sdK_(i) (nM) ± sd K_(i) (nM) ± sd K_(i)A_(t)/K_(i)A_(2a) ST 1680 97 ± 23926 ± 55 1563 ± 252  16 ST 1491 70 ± 15  10 ± 1.4 0.15 ST 1535 2.29 ±0.58 627 ± 45 107 ± 40  47 ST 2097  0.12 ± 0.033 153 ± 13 26.2 ± 6.55217 ST 1537 2.34 ± 0.69 2330 ± 588 80 ± 13 34 ST 1490 46 0.43 0.009 CGS21680 51 ± 13 ZM 241385 0.11 ± 0.03 Alloxazine  3.8 ± 2.1 DPCPX  6.5 ±0.95

[0263] TABLE 2 ST 1535 ST 2097 Reference compounds Receptors 1 μM Ki(nM) 1 μM Ki (nM) IC₅₀ (nM) Ki (nM) A₃ (h) 1580 519 IB-MECA 1.2 0.84ADO_(transporter) 24 34 NBTI 0.30 α₁(non-selective) — — prazosin 0.86α₂(non-selective) — — yohimbine 95 β₁ — — atenolol 1,770 β₂ — — ICI118551 2.3 BZD — — diazepam 12 (central) D1 — — SCH 23390 0.66 D2 — —(+)butaclamol 8.9 D3 — — (+)butaclamol 5.1 D4.4 (h) — — clozapine 156 D5(h) — — SCH 23390 0.61 GABAa — — muscimol 16 GABAb — — baclofen 50GABA_(transporter) — — Nipecotic acid 10,100 AMPA — — L-glutamate 613Kainate — — Kainic acid 77 PCP — — MK-801 2.0 P2X — — α,β-MeATP 14 P2Y —— dATPα S 22 NMDA — — CGS 19755 967 H₁ — — pyrilamine 1.3 (central) M₁ —— pirenzepina 22 M₂ — — methoctramine 34 M₃ — — 4-DAMP 3.5 M₄ — — 4-DAMP1.9 M₅ — — 4-DAMP 2.0 Choline_(transporter) — — Hemicholinium-3 12Opiate — — naloxone 1.6 (non-selective) 5-HT_(1A) — — 8-OH-DPAT 0.665-HT_(2A) — — ketanserin 2.7 5-HT_(2C) (h) — — mesulergine 1.9 5-HT₃ (h)— — MDL 72222 9.3 5-HT₄ — — 5-HT_(5A) (h) — — serotonin 79 5-HT₆ (h) — —serotonin 421 NE transporter — — protriptyline 1.1 DA transporter — —GBR 12909 5.0 5-HT transporter — 13 imipramine 4.4

In Vivo Activity

[0264] To define the activity profile (agonistic or antagonistic)possessed by the compounds of interest, their effects on motor activityin mice were examined. These were compared to these brought about by thefollowing reference compounds CGS 21680 (selective agonist of the A_(2a)receptor, EP 0 277 917) and ZM 241385 (selective antagonist of theA_(2a) receptor). It is noted that the agonists induce a depression inmotor activity, whilst the antagonists have stimulatory effects(Nikodijevicc O., et. al. J.Pharm. Exp. Ther 257, 286-94, 1991).

[0265] In table 3, the results of the effects induced by compounds ofinterest and reference, on three parameters describing spontaneous motoractivity in mice are illustrated The values of the mean and the standarderror of each parameter observed are reported. TABLE 3 Horizontalactivity Vertical activity Total distance Intervals of observation fromthe treatment Treatment 15′-45 45′-60 15′-45 45′-60′ 15′-45′ 45′-60′Controls 5992 ± 484 3148 ± 1004 356 ± 62 117 ± 40 1394 ± 148 469 ± 125CGS 21680 1608 ± 328 471 ± 254  27 ± 11  10 ± 1   504 ± 106 121 ± 73 (0.5 mg/kg) Vehicle 5890 ± 856 2259 ± 452 330 ± 96 119 ± 34 1315 ± 290412 ± 121 (10 ml/kg) ZM 241385 8706 ± 473 4148 ± 241 680 ± 64 362 ± 782280 ± 242 1022 ± 130  (15 mg/kg) ZM 241385 7035 ± 709 3505 ± 375  613 ±102 282 ± 37 1725 ± 186 783 ± 165 (30 mg/kg) ZM 241385 7790 ± 980 4241 ±407  570 ± 129 264 ± 56 2250 ± 401 1131 ± 158  (60 mg/kg) ST 1537 7494 ±565 3133 ± 250 590 ± 78 210 ± 17 1676 ± 204 677 ± 105 (2.5 mg/kg) ST1537 7203 ± 264 2844 ± 299 498 ± 77 363 ± 91 1503 ± 116 532 ± 95  (5mg/kg) ST 1537 8242 ± 847 3874 ± 295  528 ± 126 276 ± 57 2707 ± 950 843± 149 (10 mg/kg) Vehicle 5184 ± 832 1734 ± 367 123 ± 60  49 ± 25 (10ml/kg) ST 1535 5386 ± 505 1693 ± 266 282 ± 79  68 ± 21 (2.5 mg/kg) ST1535 7549 ± 508 2353 ± 199 249 ± 41  76 ± 16 (5 mg/kg) ST 1535 7434 ±526 2784 ± 345 219 ± 64  71 ± 32 (10 mg/kg) ST 1535 10524 ± 670 3321 ±363 486 ± 84 148 ± 36 (20 mg/kg)

[0266] Regarding compounds in the present invention, in particularproduct ST 1537 induces a clear increase in motor activity. In fact,independently of the product dosage administered, each of the parametersexamined is significantly increased with respect to control values.Furthermore, it is observed that compound ST 1537 is more active thanthe reference antagonist. In fact, the minimum dose of ST 1537 inducesthe same effects as these produced, with a greater dose (15 mg/kg), ofcompound ZM 241385. Also for compound ST 1535 a significant increase ofthe spontaneous motor activity in mice is observed, starting from a doseof 5 mg/Kg. Therefore, the compounds in the present invention possess anantagonistic activity towards the adenosine A_(2a) receptor.

[0267] Along with these observations, the evaluation of the eventualpresence of catalepsy in the animals, following treatment with theproducts studied (FIG. 1), confirms an antagonistic profile for ST 1537and for ST 1535. In fact, none of them brought about the appearance ofcatalepsy in mice, analogous to the reference antagonist (ZM 241385, 60mg/kg) and in contrast to that demonstrated by the reference agonist(CGS 21680, 2 mg/kg).

[0268] For compound ST 1535 the profile of antagonistic activity towardsthe A_(2a) receptor has been demonstrated also through the evaluation ofits capacity to antagonise the disappearance of catalepsy previouslyinduced by the administration of the selective A_(2a) receptor agonist:CGS21680 (FIG. 2).

[0269] The selective A_(2a) receptor agonist induced an elevated degreeof catalepsy in the animals. The product ST 1535, administered orally,significantly antagonises the appearance of catalepsy at all theobserved times, particularly when the dose administered is 10 mg/kg.This result confirms and describes the antagonistic activity profiletowards the adenosine A_(2a) receptor of preferred compound ST 1535.

[0270] The profile as selective antagonist for the adenosine A_(2a)receptor of ST 1535 was confirmed also through the study of the effectsof the compound on Haloperidol catalepsy in mice. Furthermore, throughthis evaluation the products capacity to modulate a dysfunction ofdopaminergic transmission in the nigrostriatal system was determined. InFIG. 3 it is observed that after oral administration, ST 1535 reducesthe appearance of catalepsy in mice, a behavioural manifestationpromoted by a reduction of the dopaminergic tone in the nigrostriatalsystem, following acute administration of Haloperidol. Theanticataleptic activity of ST 1535 demonstrates, indirectly, that thecompound of interest is capable of compensating the deficiency indopaminergic neurotransmission brought about in the nigrostriatal systemfollowing treatment with Haloperidol, according to the pharmacologicalcharacteristics belonging to selective antagonists of the adenosineA_(2a) receptor.

[0271] Furthermore, for the preferred compound ST 1535 it has beendemonstrated that the oral administration of the product potentiates theanticataleptic activity of treatment with ineffective doses of L-DOPAand benserazide. The results of this evaluation are reported in FIG. 4.Treatment with ST 1535 associated with ineffective doses of L-DOPA andbenserazide reduce

[0272] Haloperidol-Catalepsy, in a Dose-Dependent Manner.

[0273] These results suggest that the product of interest ST 1535 can beadministered in combination with low doses of L-DOPA for the treatmentof Parkinson's disease.

[0274] L-DOPA is commonly used for the treatment of Parkinson's disease.Yet, the use of L-DOPA becomes limited due to the appearance ofdyskinesia as a side effect (Shaw K. M. et al. “Q.J.Med” 1980 49, 283).The co-administration of ST 1535 could reduce the quantity of L-DOPA tobe administered, reducing the appearance of said side effects.

[0275] Furthermore, for the preferred compound ST 1535 an antidepressantactivity was measured. It is noted that selective antagonists of theA_(2a) receptor are being defined as new potential antidepressants (ElYacobui M. et al. British J. Pharmacol. 2001:134,68-77). FIG. 5represents the effects of ST 1535 in an animal model for depression. Thecompound reduces, in a dose-dependant manner, the time of immobility ofthe animal, in a manner similar to that observed for the antidepressivedrug Imipramine.

[0276] A further object of the present invention are pharmaceuticalcompositions comprising, as active ingredient, at least one formula (I)compound, alone or in combination with one or more other formula (I)compounds, or, said formula (I) compound or compounds in combinationwith other active ingredients useful in the treatment of the pathologiesindicated here, for example other products with activity towards theadenosine A_(2a) receptor; even in separate dosage forms or in formsadapted to combined therapies. The active ingredients in the presentinvention will be in mixtures with appropriate vehicles and/orexcipients commonly used in pharmaceutical techniques, as for example,described in “Remington's Pharmaceutical Sciences Handbook”, latestedition. The compositions according to the present invention willcontain a therapeutically effiective amount of the active ingredient.The dosages will be determined by a person skilled in the art, forexample clinicians and doctors, according to the type of pathology to betreated and the conditions of the patients, or in concurrence with theadministration of other active ingredients.

[0277] Examples of pharmaceutical compositions are those that permitoral or parenteral, intravenous, intramuscular, subcutaneous,transdermal administration. Pharmaceutical compositions suitable to thispurpose are: pills, rigid or soft capsules, powders, solutions,suspensions, syrups, solid forms for extemporary liquid composition.Compositions for parenteral administration are for example all the formsinjectable intramuscularly, endovenously, subcutaneously, in the form ofsolutions, suspensions, emulsions. We also mention liposomalformulations. Also included are the controlled-release forms of theactive ingredient, both for oral administration, pills covered withappropriate layers, microencapsulated powders, complexes withcyclodextrine, depot forms, for example subcutaneous, such as injectabledeposits or implants.

1. Compounds with formula

wherein: X is N, CH, C—R₂; R₁ is C₁-C₆ linear or branched saturated orunsaturated alkyl; R₂ is hydrogen, C₁-C₆ linear or branched saturated orunsaturated alkyl, C₆-C₁₄ aryl or C₆-C₁₄ aryl(C₁-C₆) linear or branchedsaturated or unsaturated alkyl, with the aryl group optionallysubstituted by one or more substituents, either the same or different,selected from the group consisting of halogen, hydroxy, C₁-C₆ alkoxylinear or branched saturated or unsaturated, amino, mono- or di- C₁-C₆alkyl linear or branched; R₃ is NH₂, NHR₄ R₄ is C₁-C₆ alkyl or C₁-C₆hydroxyalkyl, C₁-C₃ alkoxyalkyl, amino(C₁-C₆)alkyl, where the aminogroup is optionally substituted with one or two C₁-C₃ alkyl groups,being said alkyl groups linear or branched saturated or unsaturated,C₆-C₁4 aryl or C₆-C₁₄ aryl(C₁-C₆)alkyl, with the aryl group optionallysubstituted by one or more substituents, either the same or different,selected from the group consisting by halogen, hydroxy, C₁-C₆ alkoxylinear or branched saturated or unsaturated, amino, mono- ordi-substituted with C₁-C₆ alkyl linear or branched saturated orunsaturated; and pharmaceutically acceptable salts thereof.
 2. Thecompounds according to claim 1 wherein X is nitrogen and R₂ is n-butylin position
 2. 3. The compounds according to claim 1, wherein X isnitrogen and R₂ is phenethyl in position
 2. 4. The compounds accordingto claim 1, wherein X is nitrogen and R₂ is n-pentyl in position
 2. 5.The compounds according to claim 1, wherein X is carbon and R₂ ishydrogen in position 6 or
 7. 6. The compounds according to claim 1,selected from the group consiting of:6-amino-2,9-dimethyl-8-(triazol-2-yl)-9(H)-purine;2-butyl-9-methyl-8-(2H-1,2,3-triazol-2-yl)-9H-purine-6-ylamine;9-methyl-2-(2-phenylethyl)-8-(2H-1,2,3-triazol-2-yl)-9H-purine-6-ylamine;9-methyl-2-pentyl-8-(2H-1 ,2,3-triazol-2-yl)-9H-purine-6-ylamine.
 7. Thecompund according to claim 1, which is 6-amino-9-methyl-8-(triazol-2-yl)-9(H)-purine.
 8. Process for the preparation of compounds according toclaim 1, comprising, according to the following diagram, the followingsteps:

a) bromo-substitution at position 2 of compound a), b) substitutingbromo at position 2 of compound b) with a triazol-2-yl group to givecompound c).
 9. Pharmaceutical compositions comprising at least onecompound of claim 1 mixed with pharmaceutically acceptable excipientsand/or vehicles.
 10. Use of the compounds of claim 1 as medicaments. 11.Use of the compounds of claim 1 for the preparation of a medicament withinhibitory activity towards the adenosine A_(2a) receptor.
 12. Useaccording to claim 11, where said inhibitory activity is selective forthe adenosine A_(2a) receptor.
 13. Use of compounds of claim 1 for thepreparation of a medicament for the treatment of motor disorders. 14.Use of compounds of claim 1 for the preparation of a medicament for thetreatment of Alzheimer's disease.
 15. Use of compounds of claim 1 forthe preparation of a medicament for the treatment of Huntington'sdisease.
 16. Use of compounds of claim 1 for the preparation of amedicament for the treatment of Wilson's disease.
 17. Use of compoundsof claim 1 for the preparation of a medicament for the treatment ofParkinson's disease.
 18. Use according to claim 17, wherein theParkinson's disease has the “on-off” phenomenon, or wherein theParkinson's disease is with preponderant dyskinesia.
 19. Use accordingto claim 17, wherein said compounds are associated with L-DOPA or withone or more dopamine agonists.
 20. Use according to claim 17, where saidmedicament is useful in dopamine substitutive therapy.
 21. Use accordingto claim 17, where said disturbances are caused by drugs, trauma, toxicagents.
 22. Use of compounds of claim 1 for the preparation of amedicament for the treatment of cerebral ischaemia and/or the mechanismsassociated with neurodegenerative processes.
 23. Combination of acompound of claim 1 with L-DOPA or with dopamine agonists.
 24. Use ofthe combination of claim 23 for the preparation of a medicament usefulin dopamine-substitutive therapy.
 25. Use of the compound of claim 7 forthe preparation of a medicament with affinity towards the adenosine A₁receptor.
 26. Use according to claim 25, where said medicament is usefulfor the treatment of cognitive deficits, Alzheimer's disease, cerebralischemia, acute and chronic renal failure, renal failure induced byradiografic contrast media or by cisplatin. 27.2-bromo-4-chloro-1-methyl-1(H)-imidazo[4,5-c]pyridine. 28.4-chloro-1-methyl-2-(triazol-2-yl)-1(H)-imidazo[4,5-c]pyridine. 29.4-chloro-1-methyl-2-(triazol-1-yl)-1(H)-imidazo[4,5-c]pyridine. 30.4-benzylamino-1-methyl-2-(triazol-2-yl)-1(H)-imidazo[4,5-c]pyridine. 31.(canceled)